Method of separation and cleaning of post consumer carpet face yarn from carpet backing and yarn product produced therefrom

ABSTRACT

A process for producing a synthetic fiber composition with reclaimed post consumer carpet yarn, wherein face yarn is shaved from post consumer carpet using a shaving device to provide shaved face yarn, the shaved face yarn is reduced in size, contaminants are removed using mechanical screeners, the shave face yarn is melt filtered, and then fiber spun.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is based on U.S. Provisional Application Ser.No. 60/960,211, filed Sep. 20, 2007, the priority of which is herebyclaimed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for reclaiming and recycling postconsumer carpet. More specifically, it relates to a process forreclaiming and recycling the face yarn of post consumer carpet. Thereclaimed and recycled face yarn may be used to produce further yarn forboth textile and floorcovering applications. The reclaimed and recycledface yarn may also be used to produce articles for other non-yarnrelated applications such as injection molded articles.

2. The Prior Art

Over the last two decades, carpets for domestic and for institutionaluse have been increasingly made from synthetic polymeric materials, anda major problem has arisen with respect to disposal of suchfloorcoverings when they reach the end of their useful life. Disposal ofsuch wastes can be achieved in several ways. Two ways are either byburying in a landfill site or by burning in an incinerator facility. Inthe United States an estimated 5 billion pounds of carpet waste isdumped into landfills. Landfill sites are becoming increasingly scarceand expensive to use. Recent research has also suggested that landfillsites, located conveniently close to urban areas, are implicated inhealth problems within local populations. Incineration of waste is alsothe subject of much environmental disapproval, both by the public and insome scientific circles. Also, the energy recovered from incineration ofwaste plastics is low, particularly in terms of the volume of suchscrap.

Most of the components that make up carpet are potentially recyclable orreusable. Thus, an alternative option to dumping in landfills orincineration, and the most favored option for dealing with wasteplastics, is the recycling of these into other materials and/orproducts. However, this is not a simple option as might be firstenvisaged. Despite the public perception of “plastic” as being a singleterm to describe materials which are virtually identical, it is wellknown in the art that this is not the case, and that different types ofplastics do not easily combine together to form a coherent singlematerial. Reprocessing of mixed plastics waste streams, with no sortingof types, or addition of other materials, invariably results inmaterials of low end value. In many cases the cost of the equipmentinvolved, and the energy expended, cannot be recouped in selling on theproduct. In order to produce materials of value to the industry fromrecycled materials, a great deal of expertise has to be applied, andparticular waste streams, of known and consistent content, must beavailable.

Modern carpets generally consist of three major components. Firstly,there is the face yarn, which may be of many different fiber types ormixtures thereof. Secondly, there is a primary backing (to which theyarn is fixed, or into which it is woven), which is most commonly awoven or nonwoven fabric of a polyester or a polyolefin. Thirdly, thereis a secondary backing layer. The secondary backing tends to form themajority of the weight of the construct and is typically laminated tothe tufted carpet. The secondary backing may be a sheet or foamedmaterial, often containing a high level of coarse particle inorganicmineral fillers. Examples of base materials for the secondary backingare polyolefins, polyurethanes, PVC, bitumen and latex.

Various attempts have been made to recycle carpet scrap without priorseparation of the components. JP 60 206 868, to Ikeda Bussan, describespulverizing the waste carpet, mixing with ethylene-vinyl acetate inapproximately 50:50 ratio, and calendaring to form a backing sheet forcarpet use. The calendaring is carried out at low temperatures, suchthat the fiber component does not melt, but is instead merely dispersedthrough the product. U.S. Pat. No. 5,728,741 to Collins and Aikmanclaims a similar approach, although in this case the scrap is extrudedat high temperature, prior to calendaring, so that all components aremolten and are mixed in the melt state. Other patents refer to therecycling of unseparated carpet scrap, but using maleated polyolefinsand/or ethylene-vinyl acetate as compatibilizers. See, for example, JP05 287 139 to Teijin; JP 05 293 828 to Toyota/Mitsubishi; and U.S. Pat.No. 5,719,198 to Lear Corporation. U.S. Pat. No. 5,626,939 to GeorgiaTech. takes a low energy approach by mixing well shredded carpet scrapwith thermosetting resin precursors, and forming and crosslinking theresult mixes into “synthetic wood.” None of the above processes resultsin a melt spinnable product suitable for making fibers or yarns.

Other inventors have sought to separate the components of scrap carpetsprior to recycling same as separate product streams. These mainlyinvolve the chopping, shredding, and granulation of the carpet, followedby separation of the various polymer components via cyclone,hydrocyclone, or varying density liquid flotation baths. See, forexample, U.S. Pat. No. 5,230,473 to Hagguist and Hume; U.S. Pat. No.5,518,188 to JPS Automotive; U.S. Pat. No. 5,535,945 to BASFCorporation; U.S. Pat. No. 5,598,980 to Zimmer A. G.; and U.S. Pat. No.5,722,603 to AlliedSignal/DSM. Dissolution methods have also beensuggested; e.g., U.S. Pat. No. 5,233,021 to Georgia Tech. describes theuse of a supercritical fluid approach, in which variation of temperatureand pressure is used to sequentially dissolve the various components ofthe scrap carpet. Another alternative approach, used for carpetscontaining nylon 6, is the direct recovery of caprolactam from thecarpet scrap, as described in U.S. Pat. No. 5,169,870 to BASFcorporation, and U.S. Pat. No. 5,668,277 to DSM. Similar efforts havebeen made for monomer recovery from nylon 66 and mixtures of nylons, forexample, U.S. Pat. No. 5,526,694 and U.S. Pat. No. 5,468,900 to E.I.DuPont de Nemours and Company. The recovered monomers from theseprocesses can then be repolymerized to produce polymers for furtherfiber spinning. The above separation processes are complex in manycases, involving a number of stages, and obviously require expenditureof funds in their implementation. It may also be noted that, in many ofthese approaches, only one useable product is obtained from theseparation process, and there still remains the problem of disposing ofthe other residues from the production process.

Analysis of post consumer carpet face yarn has indicated that a varietyof contaminants may be present depending upon the exposure of the carpetduring its lifetime. Undesirable contaminants that may need to beremoved so that the reclaimed face yarn can be reused in a fiberspinning process include but are not limited to, sand, cellulose (forexample in the form of wood or paper), latex, rubber, carpet backingmaterials, gypsum and other construction materials. Other possiblecontaminants include animal hair from pets, humans and textile fabrics,and vegetable matter. All of these contaminants are typically solids ofvery large “particle” sizes in comparison to the size of individualcarpet yarn filaments. These contaminants need to be removed before thereclaimed material is suitable for fiber spinning, particularly thosecontaminants that do not melt at the fiber extrusion temperatures of thepolymer being recycled, or are incompatible with the polymer beingrecycled. Melt extrusion fiber spinning methods typically incorporatefine filtration as part of the process so that large particlecontaminants are excluded from the formed fibers. The presence of largeparticle contaminants reduces the strength of the formed fibers, makingthem unsuitable for most carpet or textile applications. In addition,high levels of contaminants, particularly of large particle size, resultin short extruder filter life such that the fiber spinning process isuneconomical due to the need for very frequent filter screen changes.

Prior to this invention there has been no method suitable for reclaimingand reuse of carpet face yarn suitable for using in a melt extrusionfiber spinning to produce carpet or textile yarns without use of theundesirable depolymerization and repolymerization methods.

Methods have been discovered of producing post consumer carpet yarnreclaim of sufficient cleanliness that the reclaimed product can then beeconomically used for further carpet yarn production without detrimentalloss of physical properties of the yarn produced.

DETAILED DESCRIPTION OF THE INVENTION

The method of the invention consists initially of identification of thechemical nature of the face yarn. The face yarn may be of severaldifferent types including but not limited to, polypropylene, polyester,e.g., polyethylene terephthalate and polytrimethylene terephthalate,polylactic acid, polyamide, e.g., nylon 6 and nylon 66, or naturalfibers such as wool.

Samples can be taken and analyzed using various analytical laboratorytechniques including both wet chemical methods and instrumentaltechniques. More preferably, a portable or hand-held identificationdevice is used and most preferably, a near infrared (NIR) spectrometeris used that is specifically designed for the identification of plasticscrap in the field.

Once the face yarn type has been identified and sorted by chemicalnature such that the type is predominantly of one type, the next step isseparating the face yarn from the carpet backing such that the separatedface yarn contains less than 5% backing material and preferably lessthan 2% backing material. The separated face yarn most preferablycontains less than 0.5% backing material. This separation can beachieved by a shaving, splitting or shearing process that can shave offthe face yarn without removing a significant amount of the carpetbacking material along with the face yarn. Commercially available carpetshearing machines could be used for this purpose or potentiallyappropriately modified for optimum use. Modification of other carpetprocessing equipment could also be used for this purpose that includes,but is not limited to, splitting equipment that used in face-to-faceweaving or fusion bonding (Ref: “Carpet Manufacture”, G. H. Crawshaw,Chaucer Press Ltd, 2002). An alternative and preferred method is the useof a hide splitting machine commonly used in the hide tanning industryfor splitting of natural or synthetic hides to a desired thickness. Ahide splitting machine typically consists of two mutually opposingrollers. The hide is passed through these two rollers and is forwardedto a splitting blade arranged in the area comprised between the tworollers. The position of the rollers relative to the splitting blade canbe modified to attain a certain thickness of hide. The pile height ofthe carpet and the thickness of the backing may vary from one piece ofcarpet to the next depending on the carpet design and construction.Thus, when “splitting or “shaving” the face yarn from the carpet. theposition of the rollers relative to the splitting blade is adjustedappropriately such that that the maximum amount of face yarn is removedwithout shaving any of the carpet backing.

The shaved and separated face yarn is then cleaned prior to re-extrusionback into fiber. The preferred method involves the initial use ofmechanical screening devices. Size reduction of the separated face yarnis beneficial in subsequent removal of contaminants; mechanicalagitation of the face yarn during the size reduction process dislodgesthe contaminants from the face yarn thereby assisting in their removal.The size reduction process also opens up twisted, cabled or barber-poleyarn allowing contaminants that might be trapped within the twisted yarnstructure to be released. A high speed, low intensity grinder ispreferred so that frictional heat in the size reduction process isminimized so that the polymer is not significantly subjected tomechanical or thermal degradation. The grinder is fitted with a screenof hole size between ⅛ inch to ¾ inch and preferably 3/16 inch to 7/16inch.

The size reduced face yarn is fed via a cyclone to a mechanicalscreening device. Airborne dust can be removed from the feed streamduring this conveyance process by the cyclone. The preferred screenertypes are those most suitable for handling light or bulky materials suchas, but not limited to, revolving screens, reciprocating screens,gyratory-reciprocating screens. Vibrating screens may also be used. Afurther option is a modification of the revolving screen type where thescreen is stationary and the material is fed through a perforatedcylindrical screen via a rotating auger. A screen opening or hole sizeof a minimum dimension of ⅛ inch to ¾ inch and preferably 3/16 inch to7/16 inch. The choice of hole dimensions is determined by the hole sizeon the grinder screen. The contaminants are removed through the holes inthe screen. The screened face yarn is discharged from the end of thecylinder. Reduced pressure flow or vacuum can be applied to the outsideof the screen to improve the efficiency of removal of the contaminantsfrom the face yarn.

The mechanically screened face yarn is now preferably cleaned or scouredfurther by an aqueous separation method or washing process. The faceyarn is preferably washed at high temperature with or withoutsurfactants. If surfactants are used, anionic-based surfactants arepreferred. A high pH condition in an oxidative reducing environment mayalso be used, however the conditions used should not be such that theface yarn is substantially degraded during the washing process. The highpH condition can be achieved by addition of an alkali, including but notlimited to, sodium hydroxide, potassium hydroxide, ammonium hydroxide,sodium or potassium carbonate, or trisodium phosphate, or mixturesthereof. The optional use of a bleaching environment can be achieved forexample by addition of thiourea dioxide. Oxidative bleaching conditionscan be achieved through use of hypochlorites, hydrogen peroxide orsodium chlorite. Commercial laundering equipment can be used for thisscouring purpose. Another non-limiting option is use of a pressurizedvessel so that the temperature may be increased above the boil forimproved cleaning efficiency and reduced washing times. If a high pHcondition is used neutralization of the wash liquor and race of the faceyarn prior to drying is preferable. This washing process may also becarried out prior to the grinding and mechanical screening if sodesired.

The substantially contaminant-free face yarn can either be convertedinto a granule or pellet form. Granule formation processes include, butare not limited to, use of a Netzsch-Condux Plastocompactor or aCalifornia Pellet Mill, melt extrusion, or a combination thereof. Pelletformation processes include melt extrusion processes which involvefeeding the material into a melt compounding extruder, using ram orcramming devices as appropriate to improve feeding efficiency, filteringthe molten material using an in-line filtration system, followed byformation of strands which are cooled and then pelletized. Underwaterpelletizers for certain polymer types can also be successfully usedremoving the need for stranding the reclaimed material. The reclaimedmaterial can then be used to prepare further synthetic fibers for use inboth textile and flooring applications.

The fiber extrusion ready reclaimed material was analyzed by carryingout a melt filtration test on a pilot-scale single screw melt extruderfiber spinning line. A filter screen pack consisting an 80×700 Dutchtwill weave screen and coarser mesh supporting screens was placed abovethe fiber spinneret. The 80×700 Dutch twill weave screen had a nominalretention of 25 microns with an absolute retention of 34 to 36 microns;(Ref: Woven Wire Cloth Reference Book, Haven & Boecker, 1990). Apressure transducer was cited above the screen pack. Blends of reclaimat various percentages in virgin PA66 with an RV=3.1 were prepared andtested using this set up and the pressure monitored.

EXAMPLE 1 Non-Inventive

A commercial reclaim post industrial melt extrusion line was purged withvirgin nylon 6 resin. Nylon 66 carpet face yarn that had been shaved offpost consumer carpet using a hide splitting machine was fed via aconveyor to the feed throat of a single screw extruder at a nominal 500lbs/hour. The nylon melt was in-line filtered through a screen packconsisting a 325 square mesh screen with coarser mesh supporting meshscreens. The 325 square mesh screen had an opening size of 43 microns.The in-line filter was of the manual filter screen change type. Pressurerise on the filter was very rapid such that the pressure exceeded theoperational limits of the filter before the reclaim material had fullypurged out the virgin nylon 6. The extrusion line was purged withfurther nylon 6 resin and a coarser screen pack consisting 80 squaremesh with coarser supporting screens was installed into the in-linefilter. The 80 square mesh filter screen had an opening size of 180microns. The nylon 66 carpet face yarn was again fed to the extruder.The operational limits of the in-line filter were again exceeded beforethe nylon 6 resin was purged out of the extruder. The extruder waspurged with virgin nylon 6 and a yet coarser screen pack consisting 3×20square mesh screens was installed in the in-line filter. The 20 squaremesh filter had an opening size of between 860 and 910 microns. Thenylon 66 face yarn was yet again fed to the extruder. The pressure riserate on the filter was approximately 0.03 psi/gram.

EXAMPLE 2 Non-Inventive

The pelletized product of Example 1 was blended with virgin PA66 of anRV=3.1 in a ratio of 25% of to 75% by weight and dried to 500 ppmmoisture. The pellet blend was further processed on a single screw meltcompounding extruder fitted with an in-line automatic filter screenchanger. The filter aperture size was 75 microns. The filtered melt wasstranded and pelletized. The level of the contaminants was such thatfilter aperture sizes smaller than 75 microns could not be used withoutexceeding the operational limitations of the machine.

EXAMPLE 3 Invention

Nylon 66 carpet face yarn that had been shaved off post consumer carpetin a similar manner to Example 1 was size reduced in a Cumberlandgranulator fitted with a 5/16″ mesh screen. The size reduced materialwas conveyed to a cyclone. The face yarn was then fed via a rotatingvalve to a screener consisting a rotating auger inside a perforatedcylindrical screen. Contaminants were removed through the screen underreduced pressure and the face yarn was conveyed by the auger through asecond rotating valve and collected. The collected face yarn wasdensified using a Condux Plastocompactor. The densified face yarn wasblended with virgin nylon 66 on a production fiber spinning line in a5:95 ratio. An in-line filter was used containing a filter screen packsimilar to that used in the melt filter test. A filter life of about 5hours was obtained.

EXAMPLE 4 Invention

Nylon 66 carpet face yarn that had been shaved off post consumer carpetin a similar manner to Example 1 was size reduced in a Cumberlandgranulator fitted with a 5/16″ mesh screen. The yarn was furtherprocessed in a similar manner to Example 3 except the face yarnthroughput was reduced and a higher vacuum was used to removecontaminants from the screener.

EXAMPLE 5 Invention

Nylon 66 carpet face yarn was shaved off post consumer carpet, sizedreduced and mechanically screened in a similar manner to Example 3. Theyarn was then washed in a commercial washing machine with Tide® laundrydetergent (registered trademark of Proctor and Gamble) and Clorox®bleach (registered trademark of Clorox Chemical Company). The cleanedyarn was tested using the melt filter test. The pressure rise wassignificantly less than Examples 3 and 4 showing the additional benefitof an aqueous washing process on the effectiveness of contaminantremoval.

The pelletized material of Examples 1 and 2, the densified reclaim ofExamples 3 and 4, and the decontaminated face yarn of Example 5 wereblended with virgin PA66 in the weight percentages shown in Table 1 andevaluated using the melt filter test described above. The results areshown in Table 1. The reclaimed material from Examples 3, 4 and 5 gavesignificantly lower filter pressure rise than Examples 1 and 2indicating that removal of contaminants in the carpet face yarn waseffective in producing a product that can be spun into carpet fiber.

EXAMPLE 6 Invention

Nylon 66 carpet face yarn was shaved off post consumer carpet, sizedreduced and mechanically screened in a similar manner to Example 3. Themechanically screened yarn was densified using a California Pellet Mill.The densified material was fed to a twin screw melt extruder fitted withan in-line melt filtration system. The melt was filtered through a 60mesh screen and pelletized. The pelletized material was subjected to themelt filter test. The results are shown in table 1.

TABLE 1 Source of reclaimed face yarn resin, % Reclaimed face ExampleNo. yarn in virgin PA66 Pressure Rise/psi/gram 1 5% 3.20 2 5% 1.10 3 2%0.60 3 10%  1.10 4 2% 0.08 5 2% 0.05 6 5% 0.09

1. A process for producing a synthetic fiber composition, comprising i.shaving face yarn from post consumer carpet by use of a shaving deviceto provide a shaved face yarn; ii. reducing the sizes of said shavedface yarn; iii. agitating said shaved face yarn; iv. removingcontaminants from said shaved face yarn by mechanical screening,washing, or a combination thereof; and v. melt filtering of said shavedface yarn to produce a recycled fiber-forming thermoplastic resin; andvi. blending at least 2 weight percent of said recycled fiber-formingthermoplastic resin with a virgin fiber-forming resin to form afiber-forming blend, wherein said fiber-forming blend provides apressure rise of 0.6 psi/gm or less when said blend (i) contains 2weight percent of said recycled fiber-forming thermoplastic resin and(ii) is subjected to a melt filter test using a Dutch twilled weavefilter screen of 80×700 nominal mesh count using a pilot-scale singlescrew extruder.
 2. The process according to claim 1, wherein said postconsumer carpet face yarn comprises nylon 6, nylon 66, polyethyleneterephthalate, polytrimethylene terephthalate, polylactic acid, orpolypropylene.
 3. The process according to claim 1, wherein said virginfiber-forming thermoplastic resin comprises nylon 6, nylon 66,polyethylene terephthalate, polytrimethylene terephthalate, polylacticacid, or polypropylene.
 4. The process according to claim 1, whereinsaid post consumer carpet face yarn comprises nylon 6, nylon 66,polyethylene terephthalate, polytrimethylene terephthalate, polylacticacid, or polypropylene; and said virgin fiber-forming thermoplasticresin comprises nylon 6, nylon 66, polyethylene terephthalate,polytrimethylene terephthalate, polylactic acid, or polypropylene. 5.The process according to claim 1, wherein said fiber-forming blendprovides a pressure rise of less than 1.10 psi/gm when said blend (i)contains 5 wt % of said recycled fiber-forming thermoplastic resin and(ii) is subjected to a melt filter test using a Dutch twilled weavefilter screen of 80×700 nominal mesh count using a pilot-scale singlescrew extruder.
 6. The process according to claim 1, wherein saidfiber-forming blend comprises at least 5 wt % of said recycledfiber-forming thermoplastic resin.
 7. The process according to claim 1,wherein said fiber-forming blend comprises about 2 to about 10 weightpercent of said recycled fiber-forming thermoplastic resin.
 8. Theprocess according to claim 1, wherein said shaved face yarn containsless than 2 weight percent carpet backing material.
 9. The processaccording to claim 1, wherein said shaved face yarn contains less than0.5 weight percent carpet backing material.
 10. The process according toclaim 1, wherein said post-consumer carpet face yarn comprisespolyethylene terephthalate, polylactic acid, nylon 6, or nylon
 66. 11.The process according to claim 1, wherein said post-consumer carpet faceyarn comprises nylon 6 or nylon 66 and said virgin thermoplastic resincomprises nylon 6 or nylon
 66. 12. The process according to claim 1,wherein said synthetic fiber composition consists essentially of saidfiber-forming blend.
 13. The process according to claim 1, wherein saidsynthetic fiber composition consists of said fiber-forming blend. 14.The process according to claim 1 wherein said contaminant removal step(iv) comprises mechanical screening and washing.
 15. The processaccording to claim 1, wherein said shaving device is a hide splittingmachine.
 16. The process according to claim 1, wherein said mechanicalscreener is selected from the group consisting of stationary screenswith rotating augers, reciprocating screens, gyratory-reciprocatingscreens and vibrating screens.
 17. The process according to claim 1,wherein step (ii) comprises grinding said shaved face yarn.
 18. Aprocess for producing a synthetic fiber composition, comprising i.shaving face yarn comprising polyethylene terephthalate, nylon 6, ornylon 66, from post consumer carpet by use of a shaving device toprovide a shaved face yarn; ii. reducing the sizes of said shaved faceyarn; iii. agitating said shaved face yarn; iv. removing contaminantsfrom said shaved face yarn by mechanical screening and washing; v. meltfiltering of said shaved face yarn to produce a recycled fiber-formingthermoplastic resin; and vi. blending at least 2 weight percent of saidrecycled fiber-forming thermoplastic resin with a virgin fiber-formingresin comprising polyethylene terephthalate, nylon 6, or nylon 66 toform a fiber-forming blend, wherein said fiber-forming blend provides apressure rise of 1.10 psi/gm or less when said blend (i) contains 5weight percent of said recycled fiber-forming thermoplastic resin and(ii) is subjected to a melt filter test using a Dutch twilled weavefilter screen of 80×700 nominal mesh count using a pilot-scale singlescrew extruder.
 19. The process according to claim 18, wherein saidfiber-forming blend comprises at least 5 wt % of said recycledfiber-forming resin.
 20. The process according to claim 18, wherein step(iv) further comprises washing said shaved face yarn with a surfactant.